Device and method for detecting faults in a shielded instrument

Abstract

A device and method for detecting faults in a shield of an electrosurgical instrument is described. The device has a relay configured to selectively interrupt power to the electrosurgical instrument, monitoring circuitry configured to monitor a shield in the electrosurgical instrument, control circuitry to control the relay, and a battery power source. The monitoring circuitry has an envelope detector and a detected average shield current detector. The monitoring circuitry is configured to compare a shield current peak value to a shield current peak threshold value, and to compare a detected average shield current value to a detected average shield current threshold value. The device is further configured to operatively couple an active electrode of an electrosurgical instrument and a return electrode to an electrosurgical generator.

What is claimed is: 
     
       1. A device for detecting insulation faults in a shielded electrosurgical instrument, comprising:
 a relay configured to interrupt power to the electrosurgical instrument; 
 monitoring circuitry configured to monitor electrical signals associated with a shield in the electrosurgical instrument; 
 control circuitry configured to control the relay; and 
 a battery; 
 wherein the device is configured to operatively couple an active electrode of the electrosurgical instrument and a return electrode to an electrosurgical generator; 
 wherein the monitoring circuitry comprises,
 a current to voltage converter configured to convert a return current of the shield into a voltage signal of the shield; 
 an envelope detector configured to detect a peak value of the voltage signal of the shield; 
 a full wave rectified average detector generating a full wave rectified average value of the voltage signal of the shield; 
 a low fault threshold detector configured to generate a low fault threshold based on a current value in the shield of the electrosurgical instrument; and 
 an output comparator coupled to the monitoring circuitry and configured to generate a fault condition when the peak value of the voltage signal of the shield is greater than the low fault threshold. 
 
 
     
     
       2. The device of  claim 1 , wherein the control circuitry comprises a warning device responsive to the monitoring circuitry. 
     
     
       3. The device of  claim 1 , wherein the control circuitry is configured to interrupt power to the electrosurgical instrument when at least one of:
 the peak value of the voltage signal of the shield is greater than a shield current peak threshold value; and 
 the full wave rectified average value of the shield is greater than an average shield current threshold value. 
 
     
     
       4. The device of  claim 1 , wherein the monitoring circuitry, the control circuitry, and the battery are connected to a common circuit ground point. 
     
     
       5. The device of  claim 1 , wherein the device is configured to operatively couple the return electrode to the electrosurgical generator. 
     
     
       6. The device of  claim 1 , wherein the device further comprises a shield current return connector configured to operatively couple the return current of the shield to the electrosurgical generator. 
     
     
       7. A system for detecting insulation faults within a shielded electrosurgical instrument, comprising:
 an electrosurgical generator; 
 an electrosurgical instrument having a shield electrically coupled to the electrosurgical generator; 
 a battery; 
 monitoring circuitry configured to monitor electrical signals associated with the shield in the electrosurgical instrument; 
 control circuitry responsive to the monitoring circuitry, configured to control a relay; 
 wherein the monitoring circuitry comprises a current to voltage converter configured to convert a return current of the shield into a voltage signal of the shield; 
 an envelope detector configured to detect a peak-to-peak value of the voltage signal of the shield; 
 a full wave rectified average detector generating a full wave rectified average value of the voltage signal of the shield; 
 and where the monitoring circuitry is configured to at least perform one of:
 (a) interrupting power to the electrosurgical instrument when the peak-to-peak value of the voltage signal of the shield exceeds a shield current peak to peak threshold value; 
 (b) interrupting power to the electrosurgical instrument when a summation of the peak-to-peak value and the full wave rectified average value is greater than an active voltage threshold value; or 
 (c) interrupting power to the electrosurgical instrument when the full wave rectified average value is greater than a variable shield current peak to peak threshold value. 
 
 
     
     
       8. The system of  claim 7 , wherein the monitoring circuitry is configured to interrupt power to the electrosurgical instrument for a predetermined period of time. 
     
     
       9. A method for detecting insulation faults in a shielded electrosurgical instrument, comprising:
 connecting a device for detecting instrument insulation faults to an electrosurgical generator, the device powered by a battery power source, the electrosurgical generator configured to deliver power to an electrosurgical instrument; 
 coupling the device to a shielded electrosurgical instrument; 
 monitoring set up signals of the shielded electrosurgical instrument, the set up signals including a connect sense and a battery power sense; 
 monitoring a return current of the shielded electrosurgical instrument; 
 determining a peak value of the voltage signal of the shield; 
 determining a full wave rectified average value of the voltage signal of the shield; 
 interrupting power to the electrosurgical instrument when at least one of the conditions are met:
 a) the peak value exceeds a shield current peak threshold or the full wave rectified average value exceeds the full wave rectified average threshold value; 
 b) a summation of the peak value and the full wave rectified average value exceeds a summation shield threshold value; or 
 c) the full wave rectified average value is greater than a variable peak-to-peak threshold value; and 
 
 controlling alarm indicators. 
 
     
     
       10. The method of  claim 9 , comprising:
 interrupting power to the electrosurgical generator when the peak value exceeds the shield current peak threshold and the full wave rectified average value exceeds the full wave rectified average threshold value.